The present invention relates to devices such as hole formers and placement rings for manhole pipe connectors cast into manhole assemblies and the like and more particularly to novel hole formers and novel two-part placement rings incorporating magnetic securement means and/or knockout means.
U.S. Pat. Nos. 3,796,406; 3,813,107; 3,832,438; 4,073,048; and 4,159,829.
Hole formers and placement ring assemblies are well known in the manhole casting field and are typically respectively utilized to accurately define an opening within a manhole base or the like and further to accurately position a manhole pipe connector gasket or hole former having a portion thereof to be embedded within the cast material.
Placement ring assemblies are conventionally formed of a metallic material and comprise first and second placement rings. A pipe connector gasket is positioned between cooperating circumferential portions of the rings and is maintained firmly clamped between the cooperating placement rings by a suitable locking member such as a wedge-shaped member inserted into an elongated slot provided in one of the placement rings which extends through a slot on a member provided in the cooperating placement ring. The placement rings can also be held together by a nut and bolt assembly. This arrangement necessitates an operation in which the wedge-shaped member must be inserted and hammered into position to assure firm engagement of the pipe connector gasket between the placement rings and subsequently to be removed by hammering. In addition, cast material as well as any other contaminants make it difficult to disassemble the placement rings after the cast member has been set.
Hole formers are used to make an opening for pipes to be mortared into place and packed in gaskets.
The present invention is directed to a novel placement ring assembly which is characterized by comprising first and second placement ring members (mandrels) which are preferably formed of a plastic, fiberglass or metal material. The inside and outside mandrels are provided with centrally located interlocking portions which inter-fit with one another when assembled to prevent the inside and outside mandrels from relative movement in mutually perpendicular directions, as well as preventing any relative rotational movement therebetween.
The inside and outside mandrels are further provided with aligned openings through which the permanent magnet of a magnet assembly is inserted. The permanent magnet of the permanent magnet assembly firmly secures the mandrel assembly and the pipe connecting gasket to the inside core or outside jacket of a casting mold.
The magnet assembly is provided with a safety stop for positioning the mandrel and a mechanical release to release the mandrel assembly from the mold assembly without the need for a prying type or impact type tool.
In view of the fact that the casting material frequently causes the mandrel members to adhere to one another, it is often necessary to pry the mandrel members apart. To facilitate the separation of the mandrel members, the inner mandrel member is provided with a plurality of knockout pads arranged at spaced intervals about the central portion of the inside mandrel which are arranged to be struck by a hammer. The knockout pads are formed of a suitable rugged metallic material of a suitable thickness which is secured to the inside mandrel by a fastener assembly. A rubber cushion is arranged between the metal knockout pad and the inside mandrel to cushion the knockout blows and thereby prevent the mandrels from being permanently damaged.
The present invention is further directed to one-piece hole formers which are provided with a magnet assembly similar to that provided in the aforesaid placement ring assembly wherein the permanent magnet is attracted to an inside core member of a mold assembly formed of a magnetically attractive material. The magnet retains the hole former in its proper position during casting and the mechanical release separates the hole former from the inside core when the cast member has set.
It is therefore one object of the present invention provided a novel mandrel assembly for placement of a pipe connector gasket for accurate placement of a pipe connector gasket within a mold assembly utilizing magnetic means which accurately positions the pipe connector gasket and the inner and outer mandrels along the mold assembly without the need for additional fastening or positioning members.
Still another object of the present invention is to provide a mandrel assembly of the type described and in which the magnetic holding means is provided with a mechanical release, eliminating the need for additional tools for removing the permanent magnet and hence the mandrel assembly from the mold assembly.
Still another object of the present invention is to provide a mandrel assembly for positioning a pipe connector gasket within a mold assembly and which is provided with shock absorbing knockout pads to facilitate separation of the mandrels after a casting operation while preventing the mandrel members from being damaged.
Still another object of the present invention is to provide a one-piece type hole former provided with magnetic means to secure the hole former in proper position when casting a member in a mold and having a mechanical release for easily separating the hole former when the cast member has set.
Still another object is to provide a one-piece type hole former having cushioning knock-out means.